1. Field of the Invention
The present invention pertains to patient interface devices structured to deliver a flow of breathing gas to a user, and, in particular, to a subnasal sealing cushion for a patient interface device that has support feature located beneath the sealing flap portion thereof
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube into the patient's esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver positive airway pressure (PAP) therapy to treat certain medical disorders, the most notable of which is OSA. Known PAP therapies include continuous positive airway pressure (CPAP), wherein a constant positive pressure is provided to the airway of the patient in order to splint the patient's airway open, and variable airway pressure, wherein the pressure provided to the airway of the patient is varied with the patient's respiratory cycle. Such therapies are typically provided to the patient at night while the patient is sleeping.
Non-invasive ventilation and pressure support therapies as just described involve the placement of a patient interface device including a mask component having a soft, flexible sealing cushion on the face of the patient. The mask component may be, without limitation, a nasal/oral mask that covers the patient's nose and mouth, a nasal mask that covers the patient's nose, a nasal cushion that rests beneath the patient's nose (such as a “pillows” style nasal cushion having nasal prongs that are received within the patient's nares or a “cradle” style nasal cushion that rests beneath and covers the patient's nares), or a full face mask that covers the patient's face. Such patient interface devices may also employ other patient contacting components, such as forehead supports, cheek pads and chin pads.
The sealing cushion typically has a support portion coupled to a sealing flap portion, which may integrated together as a single part or that may be separate components that when combined together in the final assembly provide the sealing and support functions. The patient interface device is connected to a gas delivery tube or conduit and interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head.
One particular type of sealing cushion used non-invasive ventilation and positive pressure support therapy is what is commonly known as an inflatable subnasal sealing cushion (sometimes also called an inflated subnasal auto-seal). An inflatable subnasal sealing cushion utilizes the therapy pressure to bring the sealing surface (typically in the form of a thin sealing flap) under and around the patient's nose. More specifically, this type of sealing cushion is secured under the nose and inflates to fit around the pronasale from left alare base to right alare base. The inflation around the nose compensates for varying subnasal geometries (varying nares, alares, and/or pronasale regions). Currently, the concept utilizes very little support structure for the seal itself, but requires an anchored platform from which to inflate. However, if significant force is applied directly to the sealing side of the sealing flap, the sealing element will often drastically deform and/or collapse, thereby rendering the mask useless. In addition, the prominent crease located along the subnasal sealing path between the alare and alare base makes sealing off this area very difficult, thereby causing current inflatable subnasal sealing cushions to be prone to leaking.